Storage cell battery unit equipped with a cooling device

ABSTRACT

A storage cell battery unit equipped with a cooling device that uses a circulating fluid, said battery including a housing made of plastic and constituted by a case (6) and a cover (7) heat-sealed thereon, said storage cell battery being characterized by the fact that said cooling device includes two panels (12, 13) made of plastic and heat-sealed in fluid-tight manner to respective ones of two opposite walls (3, 2) of said housing, each of the panels cooperating with the corresponding wall to delimit a circulation compartment having an inlet orifice (14) and an outlet orifice (14) for said fluid at the top of the compartment.

This is a divisional of application Ser. No. 08/143,748 filed Nov. 1,1993 now U.S. Pat. No. 5,510,207.

The present invention relates to a storage cell battery unit equippedwith a cooling device.

It is known that the different states of use of a storage cell battery(charge, overcharge, discharge) give rise to increases in temperaturewhich modify the performance levels of the battery. In this way, a 6volt, 100 Ah Nickel-Cadmium storage cell battery gives off about 450kilojoules during a discharge at 100 amps.

This has the following drawbacks:

if the battery is recharged when hot, the capacity charged is less thanthe capacity that can be stored at ambient temperature;

if the battery remains at a high temperature, its separators may bedegraded, thus reducing the life span of the battery; and

when a plurality of battery units are associated together in series orin parallel, and when they are at different temperatures, the resultingdischarge energy corresponds to the lowest performance levels, and thereis a risk of inversion at the end of discharge; it is thereforeadvisable to make the temperatures of all the grouped-together batteriesas uniform as possible; this type of problem applies particularly topowering electrical vehicles.

The means that are currently most commonly used are means causing air toflow between the battery units. In an electrical vehicle, in which thebatteries are disposed at different locations for reasons of mass and ofavailable space, it is extremely difficult to make the temperatureproperly uniform by using those means. Cooling is not very effective. Inparticular, the battery units must be spaced apart from one another inorder to allow the air to flow, and this increases the amount of spacerequired for the batteries.

It has also been proposed to place rectangular metal receptacles againstat least two opposite outside faces of the battery unit, a coolingliquid, such as water, circulating in the receptacles. It has been foundthat such an installation is still too bulky, and does not remove heatsufficiently.

An object of the present invention is to provide a battery unit equippedwith a cooling device that is both effective and compact, and that isparticularly well-suited to having a large number of battery unitsassociated together in parallel or in series.

The present invention therefore provides a storage cell battery unitequipped with a cooling device that uses a circulating fluid, saidbattery including a housing made of plastic and constituted by a caseand a cover heat-sealed thereon, said storage cell battery beingcharacterized by the fact that said cooling device includes two panelsmade of plastic and heat-sealed in fluid-tight manner to respective onesof two opposite walls of said housing, each of the panels co-operatingwith the corresponding wall to delimit a circulation compartment havingan inlet orifice and an outlet orifice for said fluid at the top of thecompartment.

In order to improve heat removal still further, the walls of the casethat carry the panels can be chosen to be thinner than conventionalwalls; the mechanical strength of the housing is then provided by thepanels themselves, which panels can be given a thickness that issuitable for this purpose.

Preferably, said wall and/or said panel is provided with a plurality ofribs that form baffles for the circulation of said fluid in saidcompartment.

The ribs are heat-sealed to the panel or to the wall during theoperation of heat-sealing the panel to the wall.

By heat-sealing the ribs, the distortion of the panel under the effectof the pressure of the circulating fluid is limited.

The ribs may be vertical or sloping.

Preferably, for each of those of said ribs which extend from the top ofsaid compartment, a space of about 1 mm to about 3 mm is left betweenthe end of the rib and the top of said compartment so as to allow gasbubbles to escape.

The panels may be heat-sealed to the cover at the same time as the case.The plastics used may be chosen from polypropylene, and polypropylenecopolymers, e.g. ABS, etc.

In a preferred embodiment, a water tank is interposed between each ofsaid orifices (inlet and outlet) and the circulation compartment.

The water tank may be integrated into the heat-sealed panel, or it maybe integrated into the case, either on the longitudinal wall carryingthe panel, or on the lateral wall that is adjacent to the wall carryingthe panel.

For reasons of compactness, it is preferable for the fluid inlet orificeand the fluid outlet orifice to be situated in the cover. The cover thencarries the pipe couplings on which fluid feed pipes can be connected.

Other characteristics and advantages of the present invention willappear on reading the following description of embodiments given by wayof non-limiting example and with reference to the accompanying drawings,in which:

FIG. 1 is a diagrammatic longitudinal elevation view of a battery of theinvention;

FIG. 2 is a diagrammatic lateral elevation view of the battery shown inFIG. 1;

FIG. 3 is diagrammatic cut-away longitudinal view showing the structureof the baffles inside a fluid circulation compartment belonging to abattery of the invention;

FIGS. 4A and 4B are fragmentary diagrams respectively showing a sectionview and a plan view of a variant of the battery of the invention;

FIGS. 5A and 5B are analogous to FIGS. 4A and 4B, for another variant ofthe battery of the invention;

FIGS. 6 and 7 are diagrammatic plan views of two variants of the batteryof the invention; and

FIGS. 8, 9, and 10 are fragmentary perspective views showing threevariants of the cooling device of the invention in more detail.

FIGS. 1 and 2 show a storage cell battery unit 1 of the invention. Inparticular the battery may comprise lead-acid, nickel-cadmium,nickel-metal hydride, or nickel-zinc storage cells. Its housing is madeof plastic, and is constituted by a case 6 and a cover 7 that areheat-sealed together. The longitudinal walls are referenced 2 and 3, thelateral walls are referenced 8 and 9, and the terminals are referenced 4and 5.

In accordance with the invention, two panels 12 and 13 made of plasticare heat-sealed in fluid-tight manner onto the longitudinal walls 2 and3. The panels co-operate with the corresponding walls to delimitfluid-circulation compartments. Input and output orifices 14 for thefluid are provided at the top of the compartments. The fluid is, forexample, a mixture of water and of ethylene glycol, with an ethyleneglycol concentration lying in the range 20% to 35% by mass. For example,the flow-rate is about a few tens of liters per hour.

To make cooling even more effective each of the walls 2 and 3 of thebattery is provided with a series of four ribs 10 and a series of threeribs 10' (cf FIG. 3) which are also heat-sealed to the panel 12, andwhich define baffles for the circulation of the fluid, as indicated bythe arrows.

Ribs 10' extend from the bottom of the compartment. Ribs 10 are not incontact with the top edge 16 of the compartment. They are offsettherefrom by in the range 1 mm to 3 mm, so as to enable gas bubbles toescape without disturbing the flow of the cooling liquid.

The ribs further offer the advantage of stiffening the panels and ofpreventing them from being distorted under the effect of the fluidpressure that is essential to the circulation of the fluid.

The number of ribs and the slope thereof may be chosen as a function ofthe characteristics desired for the flow of the fluid.

FIGS. 4A and 4B show, in more detail, the wall 2 of the case and thecover 7 heat-sealed thereon. The line of fused plastic 21 is hidden by arim 20 on the cover, which rim creates extra thickness, e.g. 2.5 mm,relative to the outside face of the wall 2, the wall in turn having athickness of 2 mm. The panel 13 is 2.5 mm thick and it delimits acompartment 22 that is 3 mm thick. At the orifice 14, the panel 13 isextended by a pipe coupling 23 having an inside diameter of 5 mm andcreating extra thickness of 13.5 mm relative to the inside face of thewall 2.

FIGS. 5A and 5B show the wall 2 and a cover 7' associated with a panel13'. The panel 13' and the wall 2 are heat-sealed simultaneously to thecover 7' thereby forming a line of fused plastic 21' hidden by a rim 20'on the cover. The orifice 14' and the pipe coupling 23' are then part ofthe cover 7'. In this case, the extra thickness created relative to theinside face of the wall 2 is only 12 mm.

In another embodiment, the rim 20 or 20' may be smaller, or else it maybe omitted.

If the thickness of the fluid feed pipe connected to the pipe couplings23 and 23' is taken into account, the overall extra thickness is notincreased in the variant shown in FIGS. 5A and 5B, whereas it isincreased in the variant shown in FIGS. 4A and 4B.

FIGS. 8, 9 and 10 show three variants of the cooling device in which thepipe coupling is incorporated into the cover of the battery.

FIG. 8 shows a battery unit case 36 having a longitudinal wall 32provided with ribs 30 and with a rim 34, a panel 35 being heat-sealedonto the ribs and onto the rim. A water tank 38 communicating with thecompartment delimited by the wall 32 and by the panel 35 is integratedby molding into the top portion of the case 36. The cover 37 has aprojection 39 carrying a pipe coupling 33 and fitting over the watertank 38; the resulting assembly is heat-sealed in fluid-tight manner.

In FIG. 9, instead of being an integral part of the case 36, the watertank 38' is an integral part of the panel 35' which is mounted andheat-sealed on the case, and which itself carries ribs 30'.

The variants shown in FIGS. 8 and 9 appear in a plan view in FIG. 6.

In the variant shown in FIG. 10, which appears in a plan view in FIG. 7,the longitudinal wall is referenced 42, and the ribs on the wall thatare designed to receive a panel 44 are referenced 40. The heat-sealededge is referenced 43.

Instead of being situated on the longitudinal wall 42 of the case, as itis in FIG. 8, the water tank 48 which communicates with the circulationcompartment is situated on the adjacent lateral wall 45. The cover 47then has a projection 49 covering the water tank 48.

Naturally, the invention is not limited to the above-describedembodiments. Without going beyond the ambit of the invention, any meansmay be replaced with equivalent means, in particular with a view tooptimizing the compactness of the cooling device.

We claim:
 1. A storage battery unit having a plurality of cells disposedwithin a housing made of plastic and having two opposite wallscomprising a case and a cover heat-sealed thereon and a cooling devicethat uses a circulating fluid, wherein said cooling device includes twopanels made of plastic and heat-sealed in fluid-tight manner torespective ones of two opposite walls of said housing, each of thepanels being shaped to cooperate with the corresponding wall to delimita circulation compartment having an inlet orifice and an outlet orificefor said fluid at the top of the compartment, at least one of saidorifices being defined by the contour of at least one of said walls andsaid panels.
 2. A storage cell battery according to claim 1,characterized by the fact that said wall and/or said panel is providedwith a plurality of ribs that form baffles for the circulation of saidfluid in said compartment.
 3. A storage cell battery according to claim2, characterized by the fact that, for each of those of said ribs whichextend from the top of said compartment, a space of about 1 mm to about3 mm is left between the end of the rib and the top of said compartmentso as to allow gas bubbles to escape.
 4. A storage cell batteryaccording to claim 1, characterized by the fact that said inlet orificeand said outlet orifice for the fluid are situated in said cover.
 5. Astorage cell battery according to claim 4, characterized by the factthat said panels and said case are heat-sealed to said coversimultaneously.
 6. A storage battery unit having a plurality of cellsdisposed within a housing made of plastic and having two opposite wallscomprising a case, a cover, and first heat sealing means for securingthe cover on the case, and a cooling device that uses a circulatingfluid, wherein said cooling device includes two panels made of plastic,and second means individually heat sealingly securing each of said twopanels in a fluid-tight manner to respective ones of two opposite wallsof said housing, each of the panels being shaped to cooperate with thecorresponding wall to delimit a circulation compartment having an inletorifice and an outlet orifice for said fluid at the top of thecompartment, at least one of said orifices being defined by the contourof at least one of said walls and said panels.